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Vitesse Fuel Gauge


slowthing
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My 1962 Vitesse 6 with non regulated, incorporated with speedo fuel gauge has developed a problem where it always reads full. Have replaced sender but didn't solve problem. Does anyone have ideas for a solution, further tests etc.

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Hi

 

If the wiring is the same as mine:

 

The fuel gauge is earthed through the sender. - Remove the green brown wire from the gauge. If its still showing "full" then there is a short on the Gauge or the gauge has a problem.

 

If nothing showing - run a spare cable to the sender - If again its showing full  its most probably the gauge that;s the problem,

 

if it shows correctly then you have a short in the car wiring 

 

Aidan

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  • 1 month later...

The Vitesse 6 - 1600 - does not have a voltage regulator.  It gets the nearest to 12V that the loom can manage direct fro the fuse box.

 

To help understanding, the sender/gauge system works this way, in both this and later models:

The gauge is fed with 12V (or an average of 10V in later models).   From there the wire goes to the sender.

The sender is a 'rheostat', a coil of resistance wire with a slider that moves with the float, so that the resistance of the coil varies as the tank fills and empties.

The gauge has a bimetallic strip that the current heats, causing it to bend.  This movement is transmitted to the needle by a mechanical linkage.

 

It would be logical (Captain) to think that the full tank will cause the sender to have the least resistance and so pass the most current, so that the gauge is heated as much as possible and moves to the "Full" end.

But it could be the other way around - an empty tank to pass max current and keep the needle at that end, but then the gauge would read "Full" with the ignition off, so I don't think they are made that way.

 

How can a gauge wired in the first way read "Full" all the time?

If there is a short to earth in the wire between the gauge and the sender.   Max current will flow, whatever the position of the rheostat.  Check the wire in the loom.    You don't need to inspect the whole thing, do this with a multimeter.    With ignition off, disconnect the wire on the gauge to the sender - Green with black trace, according to my Haynes.   Measure the resistance.  If there is none, you have a short.  You could even gild the lily by adding some fuel to the tank and seeing the resistance change as the float moves!

 

If there is a short at the sender.  One terminal is connected to earth, the other is from the gauge.   These represent the ends of the rheostat coil, one end of which will be earthed to the body of the sender.  Because there is a gasket between sender and tank, the earth is ensured by an earth wire than goes to somewhere on the bodyshell.    Reverse the wires and your gauge is shorted to earth.  Again check this at the sender with a multimeter, by measuring resistance.    If the wire from the gauge (green/black) shows none - earthed, then it is on the wrong terminal.

 

Hope that helps.

JOhn

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the early gauges in a 1600 and others has two coils and the voltage imbalance moves a magnet on the needle spindle

vehicle voltage doesnt affect them as the change is in both coils so if its 10 or14 the needle does not  change , quite the opposite of the bimetal stabilsed 

which would change reading if the voltage whilst drive kept changing  

 

from memory fitting a later bi metal sender to mine when we changed to a new tank it reversed the gauge reading, we had to cut down the original 6 hole to fit in the bayonet ring,

 

so reckon this could have  a   wrong later generation sender in the tank

 

Just a thought 

 

Pete

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